Disk Space Checking

Free Disk Space Checking in Linux

df displays the amount of disk space available on the file system containing each file name argument. If no file name is given, the space available on all currently mounted file systems is shown. Disk space is shown in 1K blocks by default, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used.

If an argument is the absolute file name of a disk device node containing a mounted file system, df shows the space available on that file system rather than on the file system containing the device node (which is always the root file system). This version of df cannot show the space available on unmounted file systems, because on most kinds of systems doing so requires very non portable intimate knowledge of file system structures.